Support shoes for tilt windows have caused many problems. Understanding what these problems are and what causes them underlies the reasons for a shoe system that I have devised to solve the problems. The way the problems are seen, though, necessarily affects the way the solutions are devised, so that my view of the problems becomes part of my invention--by setting the goals to be met.
With that understood, I have recognized that previous tilt window shoe systems suffer the following problems:
Most shoe systems require lateral withdrawal of the sash pins from the shoes, and lateral replacement of the sash pins into recesses in the shoes. Replacing the pins into the recesses is difficult, because it is hard to hold the sash in position and also see to guide the pins into the shoe recesses.
For relatively inexpensive shoe systems that do not lock when the sash is tilted and removed, sash pin withdrawal from the shoes sometimes damages the window hardware. This occurs because the sash must be slanted to withdraw its pins laterally from the shoes, and this necessarily pulls one shoe down below the other to where it can snap upward under spring tension when the lower pin is withdrawn. As the upward snap occurs, an extension counterbalance spring can contract coil-to-coil and transmit the snapping force to the top of the spring, where it can damage or dislodge the spring anchor. The snapping force can also damage the shoe.
The shoes that lock against upward movement must allow one shoe to move downward relative to the other so that the sash can be slanted for withdrawal. Lowering one side of the sash is less natural than lifting one side of the sash to achieve the slant necessary for withdrawal.
Shoes that lock sometimes fail from the abuse they suffer. People try to force them upward from a locked position, as appears to be necessary for slanting the sash; and this can break the locking mechanisms or damage the jamb liner.
Shoe systems must survive construction site environments, where the jamb liners are filled with dry wall dust, and the windows are treated more roughly than in home owner usage. Dry wall dust is abrasive and generally increases the friction of moving the shoes vertically within the jamb liners. The shoes must have enough friction to prevent hop and drop, but not so much that they stick fast when subjected to dry wall dust.
Shoes locked with their springs extended place considerable stress on the resin jamb liners. In warm weather, this stress, which can be applied for days at a time at construction sites, can deform jamb liners.
Shoe systems, although essential to tilt windows, are under competitive price pressure so that they must be made at a low cost to avoid customer price resistance. Thus, any solution to the many shoe problems must be one that can be made at a low and competitive cost.
When a sash is tilted inward from the plane of the jamb liner, the counterbalance springs pulling upward on the support shoes are relieved of the weight of the upper part of the sash, and they tend to yank the bottom of the window upward. Some shoe systems prevent this by locking the shoes when the sash is tilted, but those that do not lock give the feeling of the sash being jerked upward out of control.
Shoe systems have not been designed to take advantage of the exploratory movements that a sash remover is likely to try, in getting the sash out of the window. This happens infrequently enough so that the home owner often has forgotten the operative motions and feels his way toward movements that do work. An optimum shoe system would put no restraints on this and would not let any attempted movement cause damage. It would also make the most likely movements be the ones to succeed in removing the sash.
This list is not exhaustive of the problems of support shoes in tilt windows, but it includes the many problems that my support shoe system solves. In doing so, my shoe system aims at trouble-free functioning in all the circumstances that a tilt window system may encounter, while reducing the manufacturing costs so that the functional advantages can be competitively priced.